No significant change noted in annual nitrous oxide flux under precipitation changes in a temperate desert steppe

Abstract

As the third most important greenhouse gas, nitrous oxide (N 2 O) poses a significant threat to global warming and the ozone layer. However, the effects of precipitation changes on N 2 O emissions in arid areas remain unclear, particularly in desert steppe environments. Therefore, an in situ control experiment was conducted from July 2018 to July 2020 to examine the N 2 O emissions with changes in precipitation in the Urat Desert Steppe, northwestern China. The results showed that the N 2 O emission rate was relatively low in this desert steppe, at À0.04 to +15.0 μg N m À2 hr À1 with an annual flux of 0.20 ± 0.03 kg N ha À1 . An increasing trend of N 2 O emission was observed in the early growing season (February to June 2019) when the precipitation was increased by 40% and 60% of its natural level. In contrast, no significant change in N 2 O emissions was observed when the precipitation was decreased during the same period. During the middle and late growing season and in the nongrowing season, precipitation changes did not significantly affect N 2 O emissions. In particular, no significant change in the annual N 2 O flux was observed during the entire observation period whether the precipitation was increased or decreased. Furthermore, the results of a structural equation model showed that the most important controlling factor for N 2 O emission is an abundance of key functional ammonia monooxygenase genes of ammonia-oxidizing archaea, which are restricted by the soil NH 4 + -N content, followed by abundances of key functional NO 2 À reductase (nirK) and N 2 O reductase (nosZ) genes. In contrast, the indirect effect of soil moisture on the abundance of nosZ compensated for the direct effect of soil moisture on N 2 O emissions.These results show that the primary and secondary origins of N 2 O emissions are soil ammonia oxidation and soil denitrification processes, respectively. In these two processes, N 2 O emissions are influenced more by the abundance of key functional microorganisms than by soil moisture, which might be limited mainly by the available soil nitrogen. Overall, the N 2 O emissions in the desert steppe environment were not sensitive to precipitation changes and were regulated mainly by nitrogen-related key functional microorganisms.

Asymmetric responses of abundance and diversity of N‐cycling genes to altered precipitation in arid grasslands

“…The N 2 O produced during N transformation process is an important source of greenhouse gas, and therefore, the response of N 2 O emissions to precipitation changes is a topic of interest (Yue et al, 2022). The abundance of nosZ , a key gene involved in denitrification, represents the capacity for the transformation of N 2 O to N 2 (Petersen et al, 2012), and a higher ratio of ( norB + norC )/ nosZ abundance implies a higher potential for N 2 O release (Wang, Su, et al, 2014).…”

The Seasonal Response of N2O Emissions to Increasing Precipitation and Nitrogen Deposition and Its Driving Factors in Temperate Semi-Arid Grassland

“…The positive effects of increased N deposition on soil N 2 O emissions was suggested to result from the accelerated N cycling process. Previous studies reported positive and neutral effect of additional water supply on soil N 2 O emissions [11][12][13][14][15]. This varied response of N 2 O emissions to additional water was suggested to depend on the types of grassland and the quantity of treatments [16].…”

Impact of nitrogen and phosphorus additions on soil gross nitrogen transformations in a temperate desert steppe

“…Soil N transformations are driven by functional microorganisms (Daims et al, 2015) such as ammonia-oxidizing microorganisms, which specifically affect the soil nitrification process (Yue et al, 2021(Yue et al, , 2022. Complete ammonia oxidizers (comammox) can oxidize NH 4 + -N directly to NO 3 À -N, rather than via two steps (oxidation of ammonia to nitrite and nitrite to nitrate) which is the traditional view of nitrification (Daims et al, 2015).…”